It's been over a year since the last time I reviewed (1, 2) the Linux distribution that I use most of the time, Arch Linux. Since then, while the distro-specific innovations have slowed a bit down, maturity and stability has emerged.

I'm not exactly sure what "Stow" is, but if it's another package manager, you may very well be able to replace it over pacman. I don't imagine it being too difficult. If it's a repo to download packages from then yes you can add it. You just need to make a line in /etc/pacman.conf for it. It would look something like this:
[shadowhand] #This being the name of the repo
Server = http://arch.os-zen.net/pkg/shadowhand #This being the server address

Then go ahead and run pacman -Sy and then it should update that repo for you.